1. Field of the Invention
The present invention relates to an aircraft engine run-up hangar and, more specifically, to an aircraft engine run-up hangar incorporating improvements in the disposition of an air inlet structure, the construction of the ceiling of a test chamber, and construction of an exhaust structure through which gases are discharged from the test chamber, and capable of producing stable air currents in the test chamber.
2. Description of the Related Art
An overhauled aircraft engine or an aircraft engine of an aircraft to be placed in commission is subjected to a ground run-up in an open space for performance test. Various noise control measures have been taken for environmental protection. Generally, a noise-suppressing duct is disposed just behind the exhaust cone of the engine for, outdoor run-up. Some recent run-up method uses a building capable of entirely housing an aircraft therein and having a noise control function, which is called a noise control hangar. Generally, an air inlet structure included in a noise control hangar is incorporated into the front end part of the noise control hangar to take air into the noise control hangar. Such a noise control hangar of a front air inlet type is provided with a big door provided with an air inlet structure having current-straightening and noise control functions at its front end. This big door must be opened when carrying an aircraft into or out of the noise control hangar. The air inlet structure having current-straightening and noise control functions is inevitably long and, consequently, the big door provided with the long air inlet structure is inevitably very thick. The thickness of a big door included in a practical noise control hangar of a front inlet type is as big as 7.5 m.
Operations for opening and closing the big door provided with the air inlet structure and having a big thickness to carry an aircraft into or out of the noise control hangar need a large-scale door operating mechanism, and a large operating space is necessary for moving and storing the big door provided with the air inlet structure. Thus, the thick big door and the large operating space increase equipment costs. Moreover, the air inlet structure provides a large intake resistance and hence the back flow of exhaust gas is liable to occur in the noise control hangar. If wind blows outside across a direction in which air flows into the air inlet, it is difficult to produce uniform air currents by straightening air taken in through the air inlet and hence it is difficult to carry out the run-up of the aircraft engine under proper run-up conditions.
A previously proposed noise control hangar is provided with an air inlet in a front end part of the roof structure of the noise control hangar instead of in the front end of the noise control hangar. A noise control hangar proposed in, for example, JP-A 318696/2000 is provided with an air inlet formed in a front end part of the roof structure of the noise control hangar corresponding to the front end part of the noise control hangar, and an exhaust duct to be connected to the exhaust port of an aircraft engine and placed in the test chamber defined by the noise control hangar. Exhaust gas discharged from the aircraft engine is discharged outside through an exhaust line arranged in a back end part of the noise control hangar during the run-up of the aircraft engine. The exhaust duct must be moved every time aircrafts are changed and much labor is necessary for moving the exhaust duct. A noise control hangar disclosed in JP-A 313399/2000 has a roof structure provided with an inlet opening in a front end part thereof corresponding to the front end part of the noise control hangar, and is provided with an exhaust line extending backward and upward from the back end of a test chamber, and circulation-preventive plates having a J-shaped cross section disposed on a part of a ceiling in a back part of the test chamber to prevent the circulation of the exhaust gas.
In the prior art noise control hangar disclosed in JP-A 313399/2000, the ceiling of the noise control hangar is at a level above that of the tip of the vertical tail fin of the aircraft to enable the high vertical tail fin move under the ceiling. Therefore, the noise control hangar inevitably has a useless space in an upper region of the test chamber. Since the noise control hangar is not provided with any current straightening plates or the like for straightening air currents flowing in the useless space, the exhaust gas discharged from the engine tends to flow forward through the useless space in the test chamber, and air currents are liable to produce eddies and turbulent flows. Consequently, the exhaust gas is liable to be sucked into the engine of the aircraft and hence it difficult to carry out the run-up of the engine of the aircraft under proper conditions.
Although the circulation-preventive plates are disposed slightly in front of the tail fins of the aircraft, the exhaust gas tends to flow forward and whirling currents are liable to be produced in a region in front of the circulation-preventive plates because the large useless space extends on the front side of the circulation-preventive plates.
Since the exhaust gas produced in this noise control hangar is discharged from the back end of the test chamber directly into the exhaust line, the exhaust gas currents is accompanied by a large amount of accompanying currents, i.e., an amount as large as about four times the amount of the exhaust gas currents, during the run-up of the engine. However, any accompanying currents capable of preventing the reverse flow of the exhaust gas cannot be produced because the nose control hangar is not provided with any current straightening means for making the accompanying currents flow regularly backward.
Accordingly, it is an object of the present invention to provide an aircraft engine run-up hangar including a building defining a test chamber and having a roof structure provided with an air inlet, capable of deflecting air currents flowing through the air inlet into the building toward an aircraft housed in the building, to provide an aircraft engine run-up hangar capable of making an exhaust gas flow from a test chamber directly into an exhaust passage, and to provide an aircraft engine run-up hangar capable of producing accompanying currents capable of preventing the reverse flow of an exhaust gas in a test chamber.
According to the present invention, an aircraft engine run-up hangar includes: a building defining a test chamber capable of receiving an aircraft therein; an air inlet structure; and an exhaust structure; wherein the air inlet structure is formed in a front end part of a roof structure corresponding to a front end part of the building, the exhaust structure is connected to a rear end part of the building and defines an exhaust passage extending obliquely upward from the back end of the building, a ceiling included in the building has an inclined section sloping down backward to straighten air currents, and, a groove is formed in a middle part, with respect to the width, of the inclined section to permit the vertical tail fin of an aircraft to pass when the aircraft is carried into or out of the test chamber.
The air inlet structure is disposed on the roof structure and hence a large door for closing a large opening through which the aircraft is carried into or out of the building does not need to be provided with any air inlet structure, and the large door may be of simple construction similar to that of an ordinary soundproof door. Therefore any space for moving and storing the large door is not necessary, which is favorable to saving space necessary for installing the aircraft engine run-up hangar and is convenient in incorporating various current-straightening means into the air inlet structure. Since the exhaust structure is connected to the rear end part of the building so as to form the exhaust passage extending obliquely upward from the back end of the building, any work for moving an exhaust duct is not necessary when aircrafts are changed. Since air in the test chamber is discharged upward through the back end part of the building, the exhaust structure has a comparatively short length and needs a comparatively small space for installation behind the building, which is favorable to saving space necessary for installing the aircraft engine run-up hangar.
Since the ceiling has the inclined section sloping down backward and the groove is formed in a middle part, with respect to the width, of the inclined section to permit the vertical tail fin of an aircraft to pass when the aircraft is carried into or out of the test chamber, the inclined section can be extended in a region far below the tip of the vertical tail fin, the inclined section sloping down backward controls the accompanying currents accompanying the current of the exhaust gas so as to flow regularly backward to produce the accompanying currents capable of preventing the exhaust gas from flowing in the reverse direction in the test chamber. Thus, air currents flowing in a region above the engine of the aircraft can be regulated to ensure an air current condition proper for the run-up of the engine of the aircraft.
Preferably, the inclined section has laterally opposite parts respectively extending on the opposite sides of the groove 31 and sloping down toward right and left side wall structures. The flow of the accompanying currents decreases with distance from the groove 31. Therefore, the laterally opposite parts of the inclined section are sloped down toward the right and the left side wall structure, respectively, to prevent the reduction of the velocity of the accompanying currents in the vicinity of the right and the left side wall structures.
Preferably, a reverse flow stopping plate of a width approximately equal to that of the test chamber is suspended from the ceiling of the test chamber so as to extend in front of the vertical tail fin of an aircraft placed in the test chamber. The reverse flow stopping plate prevents the reverse from of the exhaust gas from a back part of the test chamber through an upper region of the test chamber into a front part of the test chamber.
Preferably, a vertical tail fin passing gap that permits the vertical tail fin to pass when carrying the aircraft into or out of the aircraft engine run-up hangar is formed in a middle part, with respect to width, of the reverse flow stopping plate, and the vertical tail fin passing gap can be closed or opened by a reverse flow stopping cover. The vertical tail fin passing gap is opened when the aircraft is carried into or out of the aircraft engine run-up hangar, and is kept closed during the run-up of the engine to prevent the reverse flow of the exhaust gas through the vertical tail fin passing gap.
Preferably, the reverse flow stopping plate is disposed near the back end of the inclined section of the ceiling. Thus, air currents flowing along the inclined section flow backward beyond the reverse flow stopping plate and are prevented from flowing upstream by the reverse flow stopping plate.
Preferably, an air inlet structure through which fresh air can be taken into the building is formed at a position on the roof structure corresponding to a position in front of the groove formed in the inclined section of the ceiling. Since fresh air flows through the air inlet structure into the groove, the exhaust gas is hardly able to flow forward through the groove formed in the inclined section.
Preferably, a pair of current-straightening plates for the run-up of the tail engine of the aircraft are extended down from the opposite side walls of the groove formed in the inclined section of the ceiling to straighten air currents flowing toward the tail engine of the aircraft. Although air currents flowing along the inclined section of the ceiling tend to flow laterally toward the groove and to affect the run-up of the tail engine adversely, the pair of current-straightening plates straightens the air currents laterally flowing toward the tail engine.
Preferably, the current-straightening plates for the run-up of the tail engine are formed from a metal net, a textile net, a perforated plate, a slit plate or an expanded metal. The current-straightening plates of simple construction straighten air currents and absorb sounds.
Preferably, the building of the aircraft engine run-up hangar has right and left side walls respectively having back half sections extended obliquely toward each other such that the distance between the back half sections decreases toward the back. Thus, proper accompanying currents are produced in the entire test chamber, the enhancement of noise by the repetitive reflection of sounds of specific frequencies by the opposite side walls can be prevented and noise can be reduced.
Preferably, sound-absorbing structures are incorporated into the right and the left side wall. The sound-absorbing structures absorb sounds to reduce noise.
Preferably, the exhaust structure has a width substantially equal to that of a back end part of the building. The exhaust structure having a width substantially equal to that of the back end part of the building defines an exhaust passage of a large sectional area. Therefore, the exhaust gas and the accompanying currents can be smoothly discharged and stable, backward air currents can be produced in the test chamber.
Preferably, the exhaust structure is joined to the back end of the building so as to extend over the entire width of the back end of the building. Thus the construction of the exhaust structure can be simplified, the exhaust gas and the accompanying currents can be smoothly discharged and stable, backward air currents can be produced in the test chamber.
Preferably, the exhaust structure has an upward curving or bending passage. The exhaust gas can be smoothly guided so as to be discharged vertically upward.
Preferably, the exhaust structure has main engine exhaust ducts through which exhaust gas discharged from main engines supported on the right and the left main wing of the aircraft is exhausted, and a tail engine exhaust duct through which exhaust gas discharged from the tail engine of the aircraft is exhausted. It is desirable that the exhaust duct is spaced a predetermined distance apart from the engine. The tail engine exhaust duct extends backward beyond the back ends of the main engine exhaust ducts. Thus, the main engine exhaust ducts and the tail engine exhaust duct can be spaced proper distances apart from the main engines and the tail engines, respectively.
Preferably, each of the main engine exhaust ducts has a vertical part vertically rising at the back end of the building. The vertical part of the main engine exhaust duct can be extended along the back end wall of the building and hence the construction thereof can be simplified.
Preferably, the tail engine exhaust duct defines a passage curved or bent obliquely upward toward the back. The exhaust gas can be smoothly guided and can be discharged vertically upward.
Preferably, curved connecting members connect parts of the inclined section of the ceiling extending on the opposite sides of the groove formed in the inclined section, and the opposite side walls of the groove formed in the inclined section, respectively. Air currents laterally flowing along the inclined section toward the groove formed in the inclined section into the tail engine can be straightened by the curved connecting members.